Glossary
2
bit designator
An operand that is used to designate the bit or bits of a word to be used by an
instruction.
bit number
A number that indicates the location of a bit within a word. Bit 00 is the rightmost
(least-significant) bit; bit 15 is the leftmost (most-significant) bit.
bit-control instruction
An instruction that is used to control the status of an individual bit as opposed to
the status of an entire word.
block
See
logic block
and
instruction block
.
building-block PLC
A PLC that is constructed from individual components, or “building blocks.” With
building-block PLCs, there is no one Unit that is independently identifiable as a
PLC. The PLC is rather a functional assembly of Units.
bus
A communications path used to pass data between any of the Units connected
to it.
bus bar
The line leading down the left and sometimes right side of a ladder diagram.
Instruction execution proceeds down the bus bar, which is the starting point for
all instruction lines.
byte
A unit of data equivalent to 8 bits, i.e., half a word.
call
A process by which instruction execution shifts from the main program to a sub-
routine. The subroutine may be called by an instruction or by an interrupt.
Carry Flag
A flag that is used with arithmetic operations to hold a carry from an addition or
multiplication operation, or to indicate that the result is negative in a subtraction
operation. The carry flag is also used with certain types of shift operations.
central processing unit
A device that is capable of storing programs and data, and executing the instruc-
tions contained in the programs. In a PLC System, the central processing unit
executes the program, processes I/O signals, communicates with external de-
vices, etc.
CH
See
word
.
channel
See
word
.
character code
A numeric (usually binary) code used to represent an alphanumeric character.
checksum
A sum transmitted with a data pack in communications. The checksum can be
recalculated from the received data to confirm that the data in the transmission
has not been corrupted.
clock pulse
A pulse available at specific bits in memory for use in timing operations. Various
clock pulses are available with different pulse widths, and therefore different fre-
quencies.
clock pulse bit
A bit in memory that supplies a pulse that can be used to time operations. Vari-
ous clock pulse bits are available with different pulse widths, and therefore differ-
ent frequencies.
common data
Data that is stored in a memory of a PLC and which is shared by other PLCs in
the same the same system. Each PLC has a specified section(s) of the area allo-
cated to it. Each PLC writes to the section(s) allocated to it and reads the sec-
tions allocated to the other PLCs with which it shares the common data.
communications cable
Cable used to transfer data between components of a control system and con-
forming to the RS-232C or RS-422 standards.
comparison instruction
An instruction used to compare data at different locations in memory to deter-
mine the relationship between the data.
Summary of Contents for CPM1A-20CAR-A
Page 3: ...ii...
Page 5: ...iv...
Page 9: ...iv...
Page 29: ...14 System Configuration Section 1 2...
Page 43: ...29 Unit Components Section 2 2...
Page 65: ...51 Wiring and Connections Section 3 4...
Page 123: ...Appendix B Dimensions 2 CPM1 CIF01 90 81 21 30 205 50 56 CPM1 CIF11 90 81 21 30 205 50 61...
Page 124: ...Appendix B Dimensions 3 Dimensions with Peripheral Devices Attached Approx 90 Approx 125...
Page 125: ...Appendix B Dimensions 4...
